DESCRIPTION The objective of this project is to develop a novel method of silencing the gene expression in plants. Polydactyl zinc finger proteins will be constructed from a library of zinc fingers and selected to bind a unique DNA sequence contained in the gene to be silenced. The zinc finger domain will be fused to a transcriptional repressor domain and expressed in transgenic plants to silence the expression of the target gene. An in vitro assay will be used to identify the most effective transcriptional repression domains in plants and to determine the optimum position for the zinc finger to bind. Gene silencing will be demonstrated in vivo by transiently transfecting tobacco protoplasts with the repressor construct. Transgenic plants will be generated the express a zinc finger repressor construct designed to silence an endogenous gene. Finally, zinc finger repressor proteins will be designed to silence the expression of viral proteins necessary for replication. These constructs will be used to generate transgenic plants that have increased resistance in viral infection. This technique will provide a useful method for silencing gene expression in plants to increase their disease resistance, enhance their nutritional value, or alter other agriculturally important properties. The concepts developed in this project can also be extended to alter gene expression in other eukaryotes.